through the operations several times in rehearsal, the short time available is used to the very best advantage. The operations are as a rule quite simple, nothing more than opening a shutter at the right moment, and closing it; but even simple operations require a little practice to get them just right.

Fig. 77. We know the difference between a company of recruits and the same people after they have been drilled a little; simple operations like "shouldering arms" are done clumsily at first, but smartly after drill. And after a man has learnt one kind of drill it is easier for him to learn another kind. For this reason the help of His Majesty's forces, naval or military, is specially welcome in eclipse work, and I am glad to say that it has on many occasions been very freely accorded. Eclipse tracks often